Cutting or wear elements formed from ultra hard materials such as polycrystalline diamond (PCD) used in applications such as with drill bits used for subterranean drilling are well known in the art. Such known cutting elements comprise PCD that is formed by combining synthetic diamond grains with a suitable solvent catalyst material to form a mixture. The mixture is subjected to processing conditions of extremely high pressure/high temperature (HPHT), where the solvent catalyst material promotes desired intercrystalline diamond-to-diamond bonding between the grains, thereby forming a PCD structure. The resulting PCD structure has enhanced properties of wear resistance and hardness, making PCD materials extremely useful in aggressive wear and cutting applications where high levels of wear resistance and hardness are desired.
Such cutting elements typically include a metallic substrate material that is joined to a layer or body of the PCD material during the same HPHT process that is used to form the PCD body. The metallic substrate facilitates attachment of the PCD cutting element to the cutting or drilling device being used, e.g., a drill bit used for subterranean drilling, by conventional attachment method such as welding and the like.
Techniques have been used to improve the wear resistance of the surface of the PCD material, i.e., the surface placed into cutting engagement, for the purpose of extending the service life of the cutting element. PCD is known to suffer thermal degradation at a temperature starting at about 400° C. and extending to 1200° C. and, thus conventional PCD cutting elements are known to have poor thermal stability when exposed to operating temperatures approaching 700° C. Therefore, some of the techniques used for improving the wear resistance of PCD have focused at improving the thermal stability of the PCD. One such approach has involved acid leaching an uppermost layer of an otherwise conventional PCD body to remove substantially all of the solvent metal catalyst material therefrom, while leaving the solvent metal catalyst in the remaining portion of the PCD body.
While this technique is known to improve the thermal stability of the treated uppermost layer, PCD cutters that have been treated in this manner are known to suffer from delamination and spalling during use, leading to premature failure of the cutting element and the drilling device including the same.
It is, therefore, desired that a PCD cutting element be developed that provides improved properties of wear resistance and thermal stability when compared to conventional PCD cutting elements in a manner that reduces or minimizes unwanted delamination and/or spalling, thereby providing improved cutting element service life. It is further desired that such PCD cutting element be constructed using available materials and methods.